Commit characters are not reset inside typescript object property key strings

Type: Bug

1. Create some interface type that has property keys defined
e.g.
```ts
type Fruit = 'apple' | 'banana';
type FruitCount = Record;
```
2. Create a variable that follows the type of that interface
e.g.
```ts
const someFruitCount: FruitCount = {
}
```
3. Start a new property key inside the object by typing `'` or `"`, then press a commit character, such as `.`, `;`, `(`, or `,`
4. Observe that vscode autocompletes the first suggestion inside the string.

This has been tested both in `vscode.dev` and `insiders.vscode.dev` without any extensions or configuration.

https://github.com/user-attachments/assets/a8657d94-12e3-4577-b8d4-9e0e7e8796f4

I'm happy to have a crack at fixing this bug, but I'm raising this as an issue to help visibility incase anybody else runs into this problem, or is already working on it.

VS Code version: Code 1.100.2 (848b80aeb52026648a8ff9f7c45a9b0a80641e2e, 2025-05-14T21:47:40.416Z)
OS version: Darwin arm64 24.4.0
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|Apple M2 Pro (12 x 2400)|
|GPU Status|2d_canvas: enabled
canvas_oop_rasterization: enabled_on
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: enabled
raw_draw: disabled_off_ok
skia_graphite: disabled_off
video_decode: enabled
video_encode: enabled
webgl: enabled
webgl2: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|8, 9, 7|
|Memory (System)|32.00GB (0.17GB free)|
|Process Argv|--crash-reporter-id b7d695b5-942d-4f66-81de-65c24dc54397|
|Screen Reader|no|
|VM|0%|
Extensions (39)

Extension|Author (truncated)|Version
---|---|---
Bookmarks|ale|13.5.0
vscode-monorepo-explorer|atl|0.5.1
atlascode|atl|3.8.2
cde-vscode-local-extension|atl|1.1.372
vscode-atlassian-tsserver|atl|0.0.1
Nix|bbe|1.0.1
path-intellisense|chr|2.10.0
vscode-eslint|dba|3.0.10
vscode-axe-linter|deq|4.10.7
docker|doc|0.7.0
es7-react-js-snippets|dsz|4.4.3
gitlens|eam|17.1.1
EditorConfig|Edi|0.17.3
prettier-vscode|esb|11.0.0
auto-rename-tag|for|0.1.10
copilot|Git|1.326.0
copilot-chat|Git|0.27.2
vscode-graphql-syntax|Gra|1.3.8
git-graph|mhu|1.30.0
vscode-containers|ms-|2.0.2
vscode-docker|ms-|2.0.0
debugpy|ms-|2025.8.0
python|ms-|2025.6.1
vscode-pylance|ms-|2025.5.1
remote-containers|ms-|0.413.0
remote-ssh|ms-|0.113.1
remote-ssh-edit|ms-|0.87.0
copilot-mermaid-diagram|ms-|0.0.3
remote-explorer|ms-|0.5.0
vscode-websearchforcopilot|ms-|0.1.2
abracadabra|nic|9.7.0
prisma|Pri|6.8.2
vscode-yaml|red|1.18.0
code-spell-checker|str|4.0.47
vscode-styled-components|sty|1.7.8
vscode-stylelint|sty|1.5.0
vscode-icons|vsc|12.13.0
pretty-ts-errors|Yoa|0.6.1
vscode-tsserver-trace|ypr|0.0.1

(1 theme extensions excluded)

A/B Experiments

```
vsliv368cf:30146710
vspor879:30202332
vspor708:30202333
vspor363:30204092
vswsl492cf:30256860
vscod805:30301674
binariesv615:30325510
c4g48928:30535728
azure-dev_surveyone:30548225
a9j8j154:30646983
962ge761:30959799
h48ei257:31000450
pythontbext0:30879054
cppperfnew:31000557
dwnewjupyter:31046869
pythonrstrctxt:31112756
nativeloc1:31192215
5fd0e150:31155592
dwcopilot:31170013
6074i472:31201624
dwoutputs:31242946
customenabled:31248079
hdaa2157:31222309
copilot_t_ci:31222730
e5gg6876:31282496
pythoneinst12:31285622
bgtreat:31268568
4gafe986:31271826
c7cif404:31314491
996jf627:31283433
pythonrdcb7:31303018
usemplatestapi:31297334
0aa6g176:31307128
7bj51361:31289155
747dc170:31275177
pylancecolor:31314202
aj953862:31281341
generatesymbolt:31295002
convertfstringf:31295003
gendocf:31295004

```

Tái hiện hành vi trong vscode.dev hoặc insiders.vscode.dev bằng các ví dụ TypeScript và các ký tự commit được liệt kê. Bắt đầu bằng cách lần theo hành vi completion đối với các khóa thuộc tính object được đặt trong dấu ngoặc kép, sau đó xác minh rằng việc commit một gợi ý không còn chèn completion đầu tiên vào bên trong string. Xác nhận fix với các ví dụ interface và Record đã được báo cáo.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.